Immunogenicity, Safety, And Consistency Of An Inactivated Hepatitis-A Vaccine - A Randomized Controlled Multicenter Study With 3 Different Vaccine Lots

Travellers to underdeveloped countries with endemic hepatitis A virus (HAV) infection have an increased risk to acquire this viral infection due to the decreasing prevalence of HAV infection in the western countries. We therefore conducted a controlled multicenter study to investigate the immunogenicity and safety of an inactivated hepatitis A vaccine in volunteers in order to evaluate its use for the prevention of HAV infection.A total of 204 healthy volunteers (men and women aged 18 - 40 years) were randomized in three different groups according to three different vaccine lots. Each subject was to receive a total of three doses of vaccine (720 EU) according to a 0-, 1-month primary vaccination schedule with a booster dose given at month 6. The percentage of subjects who reported side effects after the first vaccination was 49.7% and decreased after the following injections below 30%.There were no significant differences between the immunogenicity of the three vaccine lots. The incidence, severity and duration of either local or general signs and symptoms following each vaccine dose in the three study groups were similar. All side effects were classified as mild or moderate. All subjects but one had seroconverted one month after the administration of the first injection of the vaccine. The geometric mean titres (GMT) increased with each dose of vaccine administered. One month after the first injection, GMTs were 532/496/577 mlU/ml for groups 1/2/3 respectively. The booster dose administered at month 6 induced on an average a more than 10-fold increase in pre-booster GMTs to 4257/4097/4387 mlU/ml, respectively, for groups 1/2/3. There were no significant differences among the three study groups in respect to either seroconversion rates or GMTs. The results in this cohort of healthy volunteers show that the inactivated hepatitis A vaccine is safe and well tolerated.This vaccination schedule might serve as a short-term prophylaxis against hepatitis A virus infection during a travel as well as long-term prophylaxis by completing the vaccination cycle after the return from the journey.